A fyrefly resembles a large dragonfly, only completely made out of fire.

Fyreflies are commonplace on the Elemental Plane, but often emerge into the Material Plane in fiery, volcanic caves. Fyreflies attack by landing on what they want to attack and spontaneously combusting, causing instant fire damage. This is rarely damaging when only a single fyrefly does it, but one angered fyrefly typically annoys the whole swarm it belongs to (they are nearly always found in swarms), and then they all come and do it, and then the effects can become cataclysmic. They are usually peaceful, however.